Thong definition: a strip of material, especially of leather or hide, used to fasten or secure something.. See examples of THONG used in a sentence. The thong is a garment generally used as either underwear or in some countries, as a swimsuit. It may also be worn for traditional ceremonies or competitions. Viewed from the front, the thong typically resembles a bikini bottom, while at the back the material is reduced to a minimum. Thongs are triangular pants with a string that lies between buttocks and connects to waistband. Read about what is thong, benefits, and more. Learn the English definition and meaning of Thong with examples, pronunciation, and translations to enhance your vocabulary.